At present, most automobile engines are reciprocating piston engines which adopt a mixed heating cycle. Therefore, these engines have a low heat work conversion rate of about 28% to 33%. Thus, increasing the heat work conversion rate of the engines is very meaningful.
According to the existing combustion theory, the heat work conversion rate can be greatly improved by the otto cycle (i.e., constant-volume heating cycle). As shown in FIG. 8 in the accompanied drawings, when an isentropic exponent K=1.45 and a compression ratio εc=8, the heat work conversion rate ηt=60%. Although this heat work conversion rate greatly exceeds that of the existing best engine, when εc=10, the heat work conversion rate ηt can reach an amazing 70%, thereby increasing the heat work conversion rate of the engine by one grade.